Electric-furnace-regulator system



Mar. 27, 1923- 1,449,897

R. D. EVANS ELECTRIC FURNACE REGULATOR SYSTEM Filed Apr. 0 1919 WITNESSES: INVENTOR 5'06 e/VD Evans.

ATTORNEY Patented -M'ar. 27, 1923.

PATENT OFFICE.

UNITED STATES ROBERT D. EVANS, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC 8: MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRIC-EURNACE-REGULATOR SYSTEM.

Application filed April 9,

To all whom it may concern:

Be it known that I, RonEnT D. EvANs, a citizen of the United States, and a resident of \Vilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electric- Furnace-Regulator Systems, of which the following .is a specification.

My invention relates to regulator systems and particularly to regulator systems for governing the operation of electric furnaces.

One object 'of my invention is to provide a regulator system of the above-indicated character for a furnace of the movable-electrode type that shall be simple and economi cal in construction and that shall maintain the ratio of work performed by, or the ratio of heating effects of, the various electrodes substantially constant.

In the operation of electric furnaces of the movable-electrode type, and particularly if the furnaces are provided with a number of movable electrodes, for example, such as furnaces connected to a three-phase supply circuit, considerable trouble is experienced in obtaining equal heating effects by the various electrodes or in obtaining a fixed ratio of heating effects by the various electrodes. Thus, an uneven heating of the metal being treated in the furnace is very liable to be effected and, moreover, the lining of the furnace is not subjected to an even temperature and, consequently,, the length of time which the furnace may be operated without'repairs is greatly reduced. Thus, the producing of unequal heating effects by the various electrodes is liable to impair the value ofthe material being treated in the furnace and, moreover, to cause a morerapid deterioration of the furnace than would be effected if the ratio of the work performed by the vairous' electrodeswere maintained substantially constant.

In an electric furnace constructed in accordance with my invention, each movable electrode is provided with means for adjusting it in such manner that the ratio of work performed by the various electrodes may be maintained substantially constant, irrespective of the operating conditions of the furnace.

More specifically, my invention relates to a furnace having three movable electrodes connected to a transformer which, in turn,

1919. Serial No. 288,832.

is connected to a three-phase supply circuit. Each of the electrodes is provided with a motor for raising and lowering it and each motor is provided with a regluator for operating it to maintain the ratio of the heating effect produced by the associated electrode to the heating effects produced by the remaining electrodes substantially constant. Each of the regulators embodies an electromagnet having two windings which operate two switches for governing the operation of the motor associated with it. One of the windings of each of said electromagnets is energized in accordance with current flowing through the associated electrode, and the second winding of each of theelectromagnets. is energized in accordance with the potential existing between the neutral point of the transformer and the neutral point of the furnace. Thus, each electrode is controlled not only in accordance with the current flowing through the electrode but also in accordance with the potential existing between the neutral point of the transformer and the hearth of the furnace. The current passing through the second winding of each electromagnet will have a phase relation, relative to the current passing through the first winding, such as to add to, or subtract from, the energizing effect of the first winding, according to whether the associated electrode is operating to produce a greater or a less than its normal portion of the heating effect of the furnace. In the above system, it is preferable to have a star-connected secondary winding for the transformer which is connected to the electrodes of the furnace for, otherwise, an artificial. neutral point will have to be produced in a well known manner by means of auxiliary windings.

In the accompanying drawing, Figure l is a diagrammatic view of a regulator system constructed in accordance with my invention, and Figs. 2 and 3 are vector diagrams for explaining the phase relation of the currents passing through the windings of the main control magnets of the regulator.

Referring to the accompanying drawing, an electric furnace 1 is provided with three movable electrodes 2. 3 and 4, which engage the material 5 A transformer 7. having a primary winding 8 and a secondary winding 9, is procontain'ed within a health 6.

vided for connecting the three electrodes 2, 3 and 4 to a three-phase supply circuit comprising conductors 10, 11 and 12. The parts of the secondary winding 9 are preferably connected in star relation in order that t e neutral point of the transformer may be obtained without the use of auxiliary windings such as would be necessary if the parts of the secondary Winding were connected in electrodes 2, 3 and 4. The main control magnet 13 embodies a winding 16, which is energized in accordance with the current flowing through the electrode .2, and a winding 17, which is energized in accordance with the potential existing between the neu tral .point OI the transformer winding 9 and the hearth of the furnace 1. The windings 16 and 17 operate a core armature 18 which controls a contact arm 19 to selectively engage main contact members 20 and 21.

The main control electromagnets 14 and 15, respectively, embody current windings 22 and 23, which are energized in' accordance with the current flowing through the electrodes 3 and 4, and windings 24 and 25 which are energized in accordance with the potential existing between the neutral point of the transformer winding 9 and the neutral point of the furnace 1. The main 'control electromagnets 14 and 15 control the operation of the electrodes 3 and 4 in a manner similar to the control of the electrode 2 by the main control magnet 13.

A winding 26, which is inductively connected tothe transformer terminal leading to the electrode 2, is connected to the winding 16 of the main control magnet 13 to energize the winding 16 in accordance with the current passing through the electrode 2, and a similar winding 27 is associated with the transformer terminal connected to the elec trode 4 for energizing the winding 23 of the main control magnet 15 in accordance with the current flowing through the electrode 4. The two windings 26 and 27 are connected to the winding 22 of the main control magnet 14, in a well known manner, to energize the winding 22 in accordance with the current flowing through the transformer terminal which is connected to the electrode 3. The windings. 17, 24 and 25 of the main control magnets 13, 14 and 15 are connected in series with a conductor 28, which is connected to the neutral point 29 of the trans-- former winding 9, and with a conductor 30 which is connected to the hearth 6 ofthe furnace 1. Y 1 5 A regulator 31 is provided for adjusting the position of the electrode 2 and embodies, in addition. to the main control magnet 13, a motor 32 and two motor-controlling switches 33 and 34. The motor 32, which may be of any suitable type, is, preferably, a three-phase induction motor which may be connected to an auxiliary three-phase supply circuit comprising'the conductors 35, 36

and 37. It should be noted, however, that,

if so desired, the motor 32 may be connected to the three-phase supply circuit which is connected to the electrodes of the furnace 1.

The armature of the motor 32 is connected to a winding drum 38 in any suitable mantion of the motor 32in a counter-clockwise,

direction to raise the electrode 2 from the bath of material 5. The switch 34 embodies a winding 49 which is adapted to be con- 1 nected across supply conductors 43 and 44 upon engagement ofthe contact arm 19 with the main contact terminal 20. The winding 49 attracts an armature 50 which operates switch arms 51, 52 and 53 for connecting the motor 32 across the supp-1y conductors 35, 36 i and 37 to rotate it in a clockwise direction and thus effect a lowering of the electrode 2 into the bath of material 5. 1

In order to effect a quick stopping of the motor, some suitable brake must be provided to act whenever the motor is de-energized. In the drawing, a brake-wheel 54 is shown directly mounted upon the motor shaft 39 and is provided with a brake-band'55 which is under the control of an electromagnet 56. A spring 57 is provided for normally holding the brake-band 55 in engagement with the brake-wheel 54 so as to revent rotation of the motor 32 and the winding drum 38. The electromagnet 56 isconnected across twoof the motor terminals so as to be energized whenever the motor is energized and to 0ppose the action of the spring 57 so as to permit rotation of the motor 32 and the winding drum 38.

Assuming that the electrode 2 is performing more than its, normal portion ofthe work of 'the furnace 1, then there is either an increased current flow through the electrode 2 or an unbalancing of the phase relation of the currents flowing through the electrodes 2, 3 and 4, the amount of which will be indicated by the potential between the neutral point of the winding 9 and the neutral point of the furnace 1, which is the hearth 6. In case of an increased current flow, the winding 16 of the main control magnet 13 will operate the contact arm 19 to engage the'main contact terminal 21 and, in case of an unbalanced phase relation, the winding 17, which is energized in accordance with the potential existing between the neutral point of the transformer and the hearth of the furnace, will be energized to assist the winding 16 in moving the contact arm 19 to engage the main contact terminal 21. Upon engagement of the contact arm 19 with the contact terminal 21, the winding 42 is connected across the supply conductors 43 and 44 and the switch 33 is operated to connect the motor 32 across the supply conductors 35, 36 and 37 and effect rotation of it in a counter-clockwise direc tion. Consequently, the electrode 2 is raised somewhat to maintain the ratio of heating effects of the various electrodes substantially constant.

In case the electrode 2 is performing less than its normal portion of the work of the furnace, then the energization of the winding 16 is decreased or the winding 17 is energized by less current or by currenthaving a power factor such as to oppose the action of the current flowing through the winding 16 and thuspermitthe lowering of the core armature 18 and the consequent engagement between the contact arm 19 and the main contact terminal 20. Upon engagement of the contact arm 19 with the contact terminal 20, the winding 49 is connected across the supply conductors 43 and 44 to operate the switch 34. The switch 34 connects the motor 32 across the supply conductors 35, 36 and 37 for effecting rotation of it in a clockwise direct-ion. Upon rotation of the motor 32 in a clockwise direction, the electrode 32 is lowered into the bath of material 5 to adjust the ratio of work performed by the various electrodes.

Although the operation of but one electrode has been described in detail, it should be noted that the main control magnets 13,

14 and 15 are operated to simultaneously adjust the three electrodes 2, 3 and 4 to maintain the ratio ofwork performed by them substantially constant. The simultaneous operation of the three main .control magnets 13, 14 and 15 is best explained by means of the vector diagrams shown in Figs. 2 and 3. In the diagram of Fig. 2, it is assumed that a potential exists between the neutral point 29 of the transformer wind ing 9 and the neutral point of the furnace 1. In the diagram, the potential relation of the transformer windings is indicated by the vectors a, I) and c, and the potential relation of the furnace electrodes is indicated by the vectors a, b and c. The vectors a, b and 0', according to the assumption, have a neutral point 30 which isdisplaced from the neutral point 29 of the vectors a, b and c and thedistance between the neutral point 30 and 29 indicates the potential between the hearth of the furnace 1 and the neutral point of the transformer 9 and, consequently, indicates the unbalancing of the potential of the electrodes 2, 3 and 4 and the hearth. Thus, current will flow through the windings 17, 24 and 25 of the main control magnets 13, 14 and 15, which is proportional to the potential existing between the hearth and the neutral point of the transformer and, with a phase relation as indicated by the arrow, between the neutral points 29 and 30 in the diagram of Fig.

I11 the vector diagram shown in Fig. 3 of the drawing, the currents flowing through the electrodes 2, 3 and 4 are represented by the vectors 2, 3 and 4, and the currents flowing through the windings 17, 24' and 25 and the conductors 30 and 28 are represented by a vector 00 having a phase relation similar to the arrow shown in the diagram of Fig. 2, between the neutral point 30 and the neutral point 29. The vectors 2 3 and 4" respectively indicate the direction and amount of currents flowing through the windings 16, 22 and 23 of the main control magnets 13, 14 and 15, and the vector :0 represents the amount and direction of the current flowing through the windings 17, 24 and 25 of the electromagnets. Consequently, it is apparent that the currents flowing through the windings 16 and 17 of the magnet 13 will combine to effect the same pull on the armature 18 as a current 2 (F 3) which is the vector sum of the currents 2 and w. The armature of the magnet 14 is subjected to the actionof the currents flowing through the windings-22 and 24, and, consequently, is subjected to the pull of a current 3 which is equal to the victor sum of the currents 3 and 00. Likewise, the magnet 15 is subject to the pull of a current 4 which is equal to the vector sum of the currents 4 and 00. Accordingly, if equal currangement and location of parts may be made within the spirit and scope. of my invention and such modifications are intended to be covered by the appended claims.

I claim as my invention r 1. In a regulator system for a polyphase electric furnace, a plurality of movable electrodes, and means for automatically controlling said electrodes to equalize the work performed by the various electrodes with respect to each other. 4

2. In a regulator system for an electric furnace, a three-phase supply circuit, three movable electrodes connected to said circuit, and means for selectively moving said electrodes to maintain the heating effect produced by each electrode, relative to the heating effect produced by the other electrodes, substantially constant.

3. In a regulator system for an electric furnace, a three-phase supply circuit, three movable electrodes connected to said circuit, a motor for raising and lowering each of said electrodes, and means for selectively operating said motors to maintain the ratio of work performed by,the various electrodes substantially constant. 'v 4. In a regulator system for an electric furnace, a supply circuit, a plurality of movable electrodes connected to the supply circuit, a motor for raising and lowering each of said electrodes, and means controlled by the effective values of'the current and voltage supplied to the various electrodes for so controlling said motor as to equalize the work performed by the various electrodes.

5. In a regulator system for an electric v furnace, a supply circuit, a plurality of movable electrodes connected to the supply circuit, and means controlled by the current supplied to the several electrodes and by the potentials existing between the transformer connected to the several electrodes and the bath of material being treated for selectively operating said electrodes to maintain the ratio of work performed by the various electrodes substantially constant.

6. In a regulator system for an electric furnace, a transformer, three movable electrodes connected to said transformer, and means operated in accordance with the potential existing between the neutral point of the transformer and the neutral point of the furnace for automatically controlling said electrodes to maintain the ratio of work performed by the various electrodes substantially constant.

7. In a regulator system for an electric furnace, a three-phase supply circuit, three movable electrodes, a transformer for connecting the electrodes to said supply circuit, means for adjusting eachelectrode and comprising a' regulator operated in accordance with the potential existing between the neutral point of the transformer and the neutral point ofithe furnace and in accordance with the current supplied to the electrode.

8. In a regulator system for an electric furnace, a three-phase supply circuit, three movable electrodes, a transformer for con- .by the varius electrodes substantially constant.

9. In a regulator system for a polyphase electric furnace, a supply circuit, a plurality of electrodes connected to said supply circuit, means for raising and lowering said electrodes, and means for selectively operating said electrode-raising and lowering means to equalize the work performed by the various electrodes with respect to each other.

10. In a regulator system for a polyphase electric furnace, a plurality of movable electrodes, a motor for raising and lowering each of said electrodes, and means controlled by the current supplied to-the various electrodes for controlling said motors to equalize the work performed by the various electrodes with respect to each other..

11. In a regulator system for an electric furnace, a supply circuit, three movable electrodes, a transformer for connecting the electrodes to the supply circuit, and means for adjusting said electrodes in accordance with the difference in potential between the bath of material being treated and the neutral point of said transformer.

l 12. In a regulator system. for an electric furnace, a supply circuit, three movable electrodes, a transformer for connecting the electrodes to the supply circuit, and means for adjusting said electrodes in accordance with the difference in potential between the bath ofmaterial being treated and the neutral point of said transformer, and in accordance with the current supplied to the several electrodes.

13. In a regulator system for an electric furnace, a plurality of movable electrodes a transformer connected to said electrodes, a motor for raising and lowering each electrode, and control means associated with each motor and comprising a winding energized in accordance with the potential existing between the bath of material being treated and the neutral point of the transformer and a winding energized in accordance with the current flowing through the associated electrode for controlling the associated m0- tor to maintain the ratio of work performed by the various electrodes substantially constant.

14. In a regulator system for an electric furnace, a transformer, a plurality of movable electrodes connected to the transformer, a motor for raising and lowering each of said electrodes, and means comprising a relay associated with each motor for maintaining the ratio of Work performed by the various electrodes substantially constant, each of said relays comprising a winding energized inaccordance with the current supplied to the associated electrode and a winding energized in accordance with the difference in potential between the bath of material being treated and a neutral point of the transformer.

15. In a regulator system for an electric furnace, the combination comprising a plurality of movable electrodes and means for maintaining a constant current flow through the electrodes and for equalizing the poten-' tials between the electrodes and the bath of material being treated.

16. In a furnace-regulator system, the combination comprising a plurality of movable electrodes, and means comprising a,

plural-coil electromagnet operatively associated with each of said electrodes, said electromagnets being so energized as to maintain the ratio of work performed by the various electrodes substantially constant.

17. In a regulator system for an electric furnace, the combination comprising a plurality of movable electrodes and means comprising a plural-coil electromagnet operatively associated with each of said electrodes for maintaining a constant current flow through the electrodes and for equalizing the potentials between the electrodes and the bath of material being treated.

In testimony whereof, I have hereunto subscribed my name this 29th day of March ROBERT D. EVANS. 

